Rheostat



T. SPOONER.

RHEOSTAT.

APPLICATION FILED DEC I7, |919.

1,433,750.. Patented oct. 31,1922.

INVENTOR WIT ESSESZ ATTORN EY Patented Oct. 3l, 1922.

y UNITED STATES v1,433,750 PATENT OFFICE.

THOMAS SPOONER, OF PITTSBURGH, PENNSYLVANIA, ASSIGNOR TO WESTINGHOUSE ELECTRIC & MANUFACTURING COMPANY, A CORPORATION OF PENNSYLVANIA.

BHEos'rA'r.

Application led December 17, 1919.

To all whom it may concern:

Be it known that I, THOMAS SrooNEa, a citizen of the United States, and a resident of Pittsburgh, in the county of Allegheny and State of Pennsylvania,'have invented a new and useful Improvement in Rheostats, of which the following is a specification.

My invention relates to rheostats such as are commonly used in connect-ion with electrical circuits to vary the resistances thereof.

The object of my invention is to .provide a rheostat that iscompact in structure, inexpensive in manufacture and durable in use and that may be easily and conveniently*v operated.

It is customary to provide a rheostat which comprises a resistance element helically wound upon a solid cylindrical member and a movable Contact member for shunting turns of the resistor. Such rheostats, as constructed heretofore, possess a number of defects. Resistors having bodies that are solid or that are hollow and are closed at the ends heat with greatrapidity. Rigid shunting members having a single contact element wear t-he resistance element at particular points.

The rst of these undesirable features has been eliminated in my rheostat by providing a tubular resistor which is vertically mounted and is cooled by a current of air rising through it. The wear of the resistance element at particular points is avoided by using a helical spring of ring shape as the movable contact member. The coil formation of the spring which surrounds the resistor, permits it to yieldingly engage the resistance element at a number of points, thereby lessening its wear. i

For a better understanding of my invention, reference ma be had to the accompany. ing drawing in w ich Figure 1 is a View, in side elevation,`of a rheostat embodying my invention. Fig. 2 is aview in longitudinal, vertical section of the same, and Fig. 3 is a view in section of the resistor and contact mem er taken alongA the line IIL-III inf Fig. 2.

eferring particularly to Figs. 1 and. 2, a wound resistor 1 has a slidably-mounted contact member 2 for shunting turns thereof.

The resistor 1 comprises a tubular member 4. of insulating material, such, for` 3, a layer examp as asbestos paper impregnated Serial No. 345,628.`

with a solution of sodium silicate, mounted thereon, and a resistance element 5 helically wound upon the layer 4 and having its ends att-ached to clamps 6 which are electrically connected to binding posts 7.

lhe reslstor 1 is' supported by feet 8 which may be formed by cutting away strips of the material at one end of the tube and bending the remainder outwardly. The openings 1n the base of the tube formed by removal ofthe strips permit air to circulate through the tubular member 3.

The slidably mounted contact member 2, shown in Fig.r 3 of the accompanying drawing, comprises a ring 9, of molded insulat- My rheostat may be operated by connect! ing binding posts 7 to a suitable sourceI fr? electrical energy to thereby insert the entire resistor l in the circuit.

A Wire may electrically connect the binding post 13 of the contact member 2 to one of the binding posts 7, thereby permitting` f the resistance to be gradually shunted, asthe contact member 2 is raised or lowered,:j.s the case may be.

The helical form of the spring 11 provides a number of Contact points with the resistance element 5, and its resiliency lessens the wear of the element and permits the contact member to be easily moved. A finer adjustment than one turn may be obtained by slightly tilt-ing the contact member 2.

I have shown a simple and preferred form of my invention but the details may be subjected to slight modifications; therefore, I desire that only such limitations shall be imposed as are indicated in the appended claims.

vI claim as my invention:

1.In a rheostat, the combination with a coiled resistance element, of a movable contact member of helical shape surrounding said element for gradually shunting turns of the said element.

2. In a rheostat, the combination with a coiled resistance element, of a movable member of helical shape in contact with said element for gradually shunting turns Vof the said element. p p

3. In a4 rheostat, the combination with a coiled resistanceA element, of a movable contact member of helical shape surrounding said element for gradually shunting turns of said element, and means for eiecting movement of said member.

4. In a rheostat, the combination with a wound resistor, of a movable helical contact -member at least partially surrounding said member for gradually shunting turns of said resistor.

5. In a rheostat, the combination with a helically wound resistor of substantially uniform cross-section, of a slidable contactl member of helical shape surrounding said resistor for gradually shunting turns thereof.

6. In a rheostat, the combination with a vertical tubular resistor having openings at its top and bottom for the circulation of air, of means for shunting said resistor.

v7. In a rheostat, the combination with a vertical hollow resistor having openin at its topand bottom for the circulation o air,

of means for shunting said resistor.

l 8. In a rheostat, the combination a vertical tubular resistor `having openings therein for the circulation' of air, ofv meansv for shunting saidl resistor.

9. In a rheostat, the combination with a hollow vertical lresistor havlng openingscontact with sai-d element for gradually shunting turn'sof said resistance element.

12. 1n a rheostat, the combination with a tubular member, and a resistance element Wound upon said member, of a slidably -mounted holder surrounding said resistance element, said holder having a groove therein, and a. helical contactmember positioned in said -groove and in contact with said resistance element for shunting turns of said element. A

13. In a rheostat, the combination with a wound resistor of substantially uniform cross section, of a helical contact member 'surrounding said resistor and under tension to insure intimate" contact with said resistor, and means for-effecting longitudinal movement ofV said .contact member, thereby gradually shunting turns of said resistor.

14. In a rheostat, the combination with a vertical tubular member having bent flange portions at its base for supporting it and for permitting a current of air to circulate through said member, anda resistance element woundl upon said member, of a slidably-mounted grooved holder surrounding saidmember, and a helical contact .member positioned in said groove for shunting turns of said resistance element.

v15. In a rheostat, the combination with a vertical metallic tubular member having bent flange portions at lts base for supporting it and for permitting a current of air to circulate through the said member, and a resistance element Wound upon said member, of a slidably-mounted grooved holder surrounding said member, and a helical contact member positioned in saidgroove and under tension to insure intimate contact with said resistance element for shunting turns of said element.

In testimony whereof, I have hereunto subscribed my name this 8th day of December, 1919. THOMAS SPOONER. 

